The invention relates to the field of emulsions and, more particularly, to a method and apparatus for continuous preparation of high internal phase ratio emulsions characterized by small droplet size and narrow droplet size distribution.
In the petroleum industry, problems frequently arise regarding the transportation of crude oils which are viscous when produced and which, therefore, do not flow easily.
Numerous proposals have been made for transporting such viscous crude oils. These include such alternatives as heating the crude oil, adding solvents or lighter crude oils, forming an annulus of water around the crude oil, or forming emulsions of the crude oil in water.
The present invention relates to a method and apparatus for forming emulsions of the crude oil in water to obtain an emulsion which flows easily for conventional transportation. Obviously, such transportation is more efficient when the emulsion formed has a high ratio of internal phase crude oil or hydrocarbon as compared to the external phase of water. Such emulsions are known as High Internal Phase Ratio (HIPR) emulsions and are the further subject of the present invention.
Several devices are known for the preparation of HIPR emulsions. Of these devices, most involve a batch preparation procedure, such as that disclosed in U.S. Pat. No. 4,934,398 to Chirinos et al. In order to improve preparation efficiency, it is desirable to prepare the emulsion in a continuous procedure.
In conventional continuous procedures, however, large amounts of emulsifier and mixing energy are required to produce acceptable results.
For example, U.S. Pat. No. 4,018,426 to Mertz et al. discloses a system for continuous production of high internal phase ratio emulsions. U.S. Pat. No. 4,018,426 teaches that the HIPR final emulsion is formed from a homogeneously mixed preliminary dispersion in a conventional pump which provides shear forces sufficient to create an emulsion. Conventional pumps create flow patterns which vary with the properties of the fluids being emulsified as the fluid emulsifies and becomes non-Newtonian, and can result in non-uniform application of shear forces to the fluids resulting in non-uniform droplet size of the internal phase in the emulsion. Such a non-uniform droplet size has been found to adversely effect the flow characteristics of the emulsion, particularly over time.
Further, when it is desired to prepare an emulsion having relatively small droplet size, conventional pumps must be operated at a shear rate which can cause phase inversion to occur. Such high shear rates consume large amounts of power and require prohibitive amounts of emulsifiers to prevent phase inversion.
Accordingly, it is a principal object of the present invention to provide a system for forming an HIPR oil in water emulsion having a droplet size of between about 1 to 30 microns and having a narrow droplet size.
It is another object of the present invention to form such an emulsion without prohibitive amounts of mixing energy or emulsifiers, and without causing phase inversions.
It is still another object of the present invention to provide such a system which can be used to prepare emulsions having a droplet size of the internal phase less than 7 microns.
Other objects and advantages will become apparent to those skilled in the art after a consideration of the following disclosure.